Starting in 2016, travelers from four U.S. states will not be able to use their driver’s licenses as ID to board domestic flights—a pretty major development considering an estimated 62 percent of Americans don’t have passports.

The standard licenses from New York, Louisiana, Minnesota, New Hampshire, and American Samoa are considered “noncompliant” with the security standards outlined in the Real ID Act, which was enacted back in 2005 but is being implemented in stages. Why are these specific licenses deemed sub-par? In these five places, getting a license doesn’t require proof of citizenship or residency.

The new rules will go into effect sometime in 2016 (the exact date has not been announced), and there will be a three-month forgiveness period, during which people with these licenses will be warned that their IDs are no longer valid for flights.

Here’s the breakdown: if you’re from one of these states, “acceptable” IDs include passports and passport cards, as well as permanent resident cards, U.S. military ID, and DHS trusted traveler cards such a Global Entry and NEXUS.

The TSA will also accept Enhanced Driver’s Licenses, the kind that are currently used to replace passports for travel to and from Canada, Mexico, and the Caribbean. Of the noncompliant states, only New York and Minnesota issue enhanced licenses.

For families from these states, at least children under 18 years old do not need ID when traveling with a companion.

It costs an adult at least $110 to get a first passport or to renew an old one, though there are ways around the passport option in two states. New York will offer an enhanced ID that passes muster with the Transportation Security Administration, though it will cost $30 extra on top of normal application fees. Minnesota offers one too, but Louisiana and New Hampshire do not.

The Real ID Act of 2005 was a post-Sept. 11 measure that tightened access to federal facilities and created a national standard for state-issued IDs; Time reports the four states missed the cut because they either lack an appropriately rigorous verification process for identities or immigration status or because the physical cards they produce don’t contain certain security features. The law has been rolled out by the Department of Homeland Security in several phases and the rules governing air travel could take effect next year, though that date is very much up in the air.

Travelers from the territory of American Samoa are also affected; they must present a passport or other approved documents. All U.S. children under 18 may continue to travel domestically without presenting identification.

Getting straight answers about how and when the rule will be implemented isn’t easy as government regulators and members of the travel industry avoided discussing the looming rules change.

The TSA, which oversees airport security, declined to comment. The DHS website doesn’t lay out specifics about the rules, but claims the public will have sufficient notice.

“DHS will ensure the public has ample advanced notice before identification requirements for boarding aircraft change. That notice will include information on the process for individuals with a non-compliant driver’s license or identification card to be able to travel by aircraft,” reads a section of the DHS website.